Method for making electrical coils



NOV. 29, 1949 p, AfDQRlQ 2,489,867

METHOD FOR MAKING ELECTRICAL COILS Filed June 13, 1946 Timing Mechanism 3 INVENTOR.

H BY 21 I Pity'Orio A TTORNEYS Patented .Nev.-2a,-.-1949 METHOD FOR MAKING ELECTRICAL COILS Pat A. DOrio, Oak Park, Ill., aacignor to Belmont Radio Corporation. Chicago, 111., a corporation of Illinois Application June 13, 1946, Serial No. 816,551

' 5 Claims. (01. 154-80) The present invention relates to a method and apparatus for making electrical coils and more particularly to a process and apparatus for manufacturing built-in loop type antennas. Specifically, the present invention is an improvement on my prior application, Serial No. 650,063, filed February 25, 1946, and assigned to the same assignee as the present application.

. Loop antennas of the built-in type have been extensively employed in recent years in the radio industry. Such antennas or coils are adapted for assembly as an integral part of a radio receiving set and since they are usually placed within the radio cabinet, the size or bulk of the coil directly affects the size of the cabinet and hence, the over-all cost of the set. An electrical coil or winding which is suitable for use as a built-in type of radio antenna usually comprises a flat, either elliptical, circular or rectangular, winding which is often referred to as a pancake winding in which a suitable electrical conductor is spirally wound one turn on the outside of the next turn with the adjacent turns of the conductor insulated from one another either by air or a suitable insulating material. In accordance with the invention disclosed and claimed in my prior copending application referred to above, an insulated conductor is employed or an uninsulated conductor with intervening layers of insulation between the turns, and a coil is formed by winding such a conductor preferably insulated with a thermoplastic or a thermosetting insulating material with the adjacent turns arranged so that the insulation thereof is in engagement. A selfsupporting coil is made by heating the insulation by passing current through the winding thereby causing the insulation of adjacent turns to cohere.

In the manufacture of windings or coils in accordance with the invention disclosed in my above-mentioned copending application, the finished loop has a predetermined amount of inductance. It sometimes becomes necessary to make a fine adjustment in the inductance of the loop by pulling a short length of the end of the winding away from the adjacent portion of the winding. When this is done with a coil where the insulating layers are fused together, there occasionally results some exposure of the conductor due tothe coherence of the adjacent insulating members which might cause a short circuit if the bare parts touched each other accidentally. It would be desirable to provide a method and apparatus whereby such fine adjustment of the inductance by pulling away the end of the conductor could be accomplished without impairing the insulation of the conductor.

Accordingly, it is an object of the present invention to provide a new and improved method It is another object of the present invention to accomplish the desired result mentioned above.

It is a feature of the present invention to provide an apparatus for constructing a self-supporting winding in which a portion of the winding adjacent the end thereof is cooled even though the winding is heated to cause fusing or coherence of the mutually engaging insulation portions of the conductor whereby fine adjustments of the inductance may be made by pulling away the end of the wire or conductor without impairing the insulation.

Further objects and advantages of the present invention will become apparent as the following description proceeds and the features of novelty which characterize this invention will be pointed out with particularity in the claims annexed to and forming a part of this specification.

For a better understanding of the present invention reference may be had'to the accompanying drawing in which:

Fig. l is a top plan view of a pancake type electrical winding made in accordance with the present invention;

Fig. 2 is a somewhat schematic view of apparatus employed in carrying out one step of the process of the present invention;

Fig. 3 is an enlarged perspective exploded view of a portion of the apparatus of the present invention as employed in Fig. 2;

Fig. 4 is a side view of one portion of the apparatus shown in Fig. 3. more clearly to bring out the present invention;

Fig. 5 illustrates the heating step in the process of manufacturing the electrical winding of Fig. 1; I

and

Fig. 6 is an enlarged view of a portion of the winding shown on the mandrel in Fig. 3 to illustrate how fine adjustments in the inductance thereof are made.

The process and apparatus for making an electrical coil is illustrated in connection with the manufacture of the pancake coil wherein a conductor insulated with a thermosetting or thermoplastic insulating material is spirally wound on an insulating supporting member positioned between two insulating plates defining a mandrel. The winding is made self-supporting by passing a high current therethrough for a predetermined time to cause coherence of the insulation of adjacent turns. In order that fine adjustments of the inductance of the winding may be made, a heat conducting member is positioned in one or more of the insulating plates forming the mandrel so as to engage the winding adjacent the end where adjustment of the inductance can be made so that the inductance can be changed by pulling away a small length of wire which has not fused with the adjacent layer by virtue of and apparatus for manufacturing electrical coils 00 the heat conducting member.

or windings.

Referring now to Fig. 1 of the drawing, there is illustrated an electrical winding III manufactured in accordance with the present invention. This winding comprises a length of electrical conductor II, spirally wound in elliptical form and having a thickness in a direction normal to the drawing of Fig. 1 of one turn. The electrical conductor II in the coil III is illustrated as' having a coating of insulating material I2 thereon. It should be understood that although the invention is specificallydisclosed in connection with manufacturing an antenna winding of elliptical shape it couldequally well be used Wfioduce a winding of circular or some other shape. It should also be understood that this invention could "be applied to the manufacture of any coil in which the adjacent turns are so arranged as to have their insulated surfaces in physical engagement.

Preferably the winding I is formed from insulated wire I I which is built up or wound between a pair of insulating plates I3 and I4 forming the mandrel of a winding machine I5 schematically indicated in Fig. 2 of the drawing. These plates I3 and I4 are shown in greater detail in Fig. 3 of the drawing and preferably comprise a pair of smooth finished fiat insulating members formed of "Bakelite" or the like. The plate I3 is provided on one side with a. stub shaft I6 which may be inserted into the hollow end of the rotary shaft ll of the winding machine I5 driven by a suitable winding motor I8 through suitable pulleys I9 and and a belt 2|. The shaft I1 is illustrated as being rotatably mounted in one or more bearings such as indicated at 22. In order that the stub shaft IE .on plate I3 may be removably connected with the winding machine shaft I1 a suitable set screw 23 may be employed in shaft I1 at its hollow end whereby rotation of the shaft I1 causes rotation of the shaft I6 and consequently also rotation of the mandrel comprising the plates I3 and I4.

As is best shown in Fig. 3 plate I3 is provided with a raised portion 24 on the side adjacent plate I4 which serves as the core or spool upon which the wire II is wound to form electrical coil I0. Although the portion 24 is referred to as a raised portion integral with the plate I3, it may also comprise a separate removable member if desired. It will furthermore be understood that the portion or core 24 may have any desired shape depending upon the form of the coil I0. However, since an elliptical coil is illustrated in Fig. l of the drawing, the portion or core 24 is illustrated as of elliptical shape to conform with the central opening in the winding ID of Fig. 1. The plate I3 is also provided with a pair of aligning pins 25 extending from the raised portion 24 in a direction a parallel with the axis of the stub shaft I 6. The

' cated in Fig. 3 of the drawing. Fastening means 2Iisalso provided at its other end with a manipulatingmeans such as a knurled knob 21b so that the two plates I3 and I4 can readily be fastened together in the manner indicated in Fig. 2 of the drawing or taken apart as shown in Fig. 3. The

width of the winding space defined between plates I3 and I4 is controlled by the raised portion or core 24 of plate I3. This space is adjusted so as to be Just large enough to accommodate a single width ofthe insulated wire II in the event that an insulated wire is employed. With this ar-. rangement it is clear that the wire will be held in place since the space between plates I3 and I4 insures proper positioning thereof. It should be understood that if the diameter of the wire to be employed in constructing the electrical'winding III is to be greater than the amount core 24 is raised from the surface of plate I3, a suitable lo shim not shown of the same configuration as raised portion 24 may be inserted between the plates, the shim being provided with suitable openings cooperating with the aligning pins 25 to support the same on the plate I3. By employing an 15 assortment of shims of various sizes electrical windings employing any size wire may be constructed with the same winding apparatus. a As illustrated in Fig. 2 of the drawing the wire I2 is spirally wound on the core or raised portion 24 between plates I3 and I4 from a suitable supply reel 28 rotatably mounted in any suitable manner as is schematically indicated.

In order to anchor the ends of the winding I0 and so that they may be available to carry out a 25 subsequent step in the process of manufacture to be described hereinafter, plate I4 is provided around the outer edge thereof with a series of notches 29 best shown in Figs. 3 and 5 of the drawing, and a pair of split pegs 30 which extend from the side of plate I4 opposite the side thereof adjacent plate I3. When it is desired to start a new coil ID the end I Ia of the wire I I from the reel 28 is placed between plates I3 and I4 and allowed to extend out of one of the notches 29 as is shown in Fig. 5 of the drawing. This end He of wire II is anchored to the one of the split pegs 30 most closely adjacent to the particular notch 29 through which the wire II extends. It will be obvious that the depth of the notches 29 0 should be such as to extend to the outer periphery of the portion 24 whereby the end of the inside turn of the coil I0 may be brought out at the bottom of a particular one-of these notches 29. The reason why a plurality of notches such as 29 are provided is to permit one to manufacture coils having different predetermined values of inductance with the same apparatus. To accomplish this the winding may require a fractional turn and accordingly for coils having different inductances it is desirable to have a series of notches 29 judiciously spaced around the periphery of plate I4. In production, it has been found that the coils made by this process have uniform inductance thus requiring a minimum adjustment when placed in the radio sets for which they were designed. Also it is sometimes desirable to provide a winding having more than two terminals as, for example, a radio frequency transformer. This is. another'reason why it is desirable to provide a plurality of notches 29 through which the ends of the wires leading to the plurality of terminals may be brought out. Upon winding the desired number .of turns between plates I3 and I4 the insulated conductor II is cut oil and the other end IIb brought out through another one of the notches 29 and fastened to the other split peg 30 as is shown in Fig. 5. In order to simplify the disclosure the invention is illustrated in connection with manufacturing an electrical winding I0 having but two tus comprises a mandrel including plates I3 and ll of insulating material, the particular shape or construction thereof forms no part of the present invention and any suitable apparatus for winding the conductor to produce the winding it which may be of any configuration may be employd so long as the adjacent turns have their insulation in physical engagement.

If it were desired to remove the completed winding from between plates l3 and H immediately following the winding operation, it is obvious' that the coil would not retain its desired shape and the adjacent turns would separate from one another. In prior art arrangements various rather complicated processes were employed for causing the insulation of the adjacent turns to cohere to each other whereby a coil which is completely self-supporting without any additional supporting structure is obtained. In accordance with my above-mentioned copending application, this is accomplished in a simple and inexpensive manner by employing an insulated wire II, the insulation I! of which preferably comprises a thermoplastic insulating material but might conceivably also comprise a thermosetting insulating material. A very suitable thermoplastic insulating material for this purpose is polyethylene which is extensively used for insulating electrical conductors. In accordance with the present invention the ends Ila and lib of winding i0, while still positioned between plates i3 and H, are connected across a suitable source of electrical potential such as an alternating current generator generally indicated at 3! in-Fig. 5 of the drawing through a suitable control rheostat 32, and a control switch or circuit breaker 33 having associated therewith a timing mechanism 34. The timing mechanism 34 is of a type that will cause switch33 to open following closurethereof within a predetermined time which may be adjusted in any desired manner. The particular construction of the switch 33 and the timing mechanism 34 forms no part of the present invention and they have been only schematically shown in Fig. 5 of the drawing. The essential feature of this construction is that the switch 33 opens to interrupt the current flowing in winding in following a predetermined time of closure of switch 33. During this heating operation described in greater detail hereinafter the plates l3 and M in assembled condition with the winding l positioned therebetween are preferably removed from the winding machine l illustrated in Fig. 2 of the drawings so that additional windings may be produced by employing additional mandrels whereby the winding machine I5 may be maintained in continuous operation.

By passing a predetermined amount of current through the winding I3 fora predetermined period of time a heating effect is produced which heats the thermoplastic insulation to a desired extent to soften the same so that it coheres with other insulation similarly heated and in engagement therewith whereby upon cooling thereof coherence or fusing of the insulation between adjacent turns is obtained. The amount of current and the length of time that it is applied is critical since if too great a heating effect is produced the thermoplastic insulating material may melt away from the conductor entirely and if an insufllcient heating effect is produced this will result in poor cohesion between the turns of winding Hi. It is obvious that the heating eflect required depends 'upon the thermal lag of the winding it and plates is and I4 and the melting point of the thermoplastic insulating material i2. As an example, for a particular size of the mandrel comprising the plates i3 and It the desired heating effect for polyethylene insulation on a particular size of wire was found to be produced by passing 100 amperes through the winding I. for five seconds. Adjustment of the rheostat 32 controls the magnitude of the current and the timing device 34 can be set to give any desired time of current application with respect to the winding l0. Upon the completion of the heating operation and opening of the switch or circuit breaker 33, the winding It may be almost immediately removed from between the plates l3 and I3, and due to the thermoplastic welds between adjacent turns of the winding a substantially unitary construction of winding is provided which holds its configuration permanently with the turns thereof retained in spaced and insulated relationship. If any distortion of the windings is caused by expansion from the heating effect such distortion is uniform. No other supporting means is required and the method of constructing the antenna is not only very simple and inexpensive but it lends itself admirably to mass production methods.

The arrangement described thus far is disclosed and claimed in my copending prior application referred to above.

In view of the fact that the engaging layers of insulation of the winding it are fused together or caused to cohere, difliculty may be encountered in making fine changes in the inductance of the winding by pulling away a short portion of one of the ends of the winding. Due to such fusing or coherence, it is possible that in some cases when pulling away a portion of the end of the conductor that the insulation is torn from one of the conductors so as to expose the conductor itself with the possibility of accidentally short circuiting the winding. In accordance with the present invention, the possibility of impairing the insulation by making fine adjustments in the inductance is completely eliminated. This is accomplished by providing cooling means in at least I one of the insulating plates l3 or it. It is immaterial as to which of the plates the cooling means are associated with and as illustrated in Fig. 3 of the drawing, the cooling means are associated with insulating plate i3 and comprise heat conducting cylinders such as copper or aluminum slugs indicated at 36 and 31 in Figs. 3 and 4 of the drawing. In Fig. 3 the positions of the slots 23 in plate H are indicated by dotted lines on plate i3 and it is observed that the copper slugs or heat I conducting means 33 are placed adjacent the bottom of these slots while the heat conducting means 31 are placed adjacent the top of some of these slots. With this arrangement, the ends of the winding, or at least a portion adjacent the 30 ends, is cooled by the associated heat conducting means 36 or 31. The reason why a plurality of heat conducting means such as 35 and 31 are provided is to take care of the different windings which may be manufactured through employing (5.3 the mandrel illustrated in Fig. 3 of the drawing. It will be understood that if only a particular winding is to be manufactured that many of the slots 23 can be dispensed with and perhaps only a single cooling means at one end of the winding 70 is sufllcient. However, with the illustrated arrangement, the mandrel may be used for manufacturing coils of varied inductances which are still capable of fine adjustment of the inductance without impairing the insulation.

In the event that still greater cooling is desired than is provided by the cooling means comprising the conducting cylinders 36 and 31 extending through the insulating plate 13, conducting fins connected to the ends of the cylinders on the side of plate I! opposite that engaged by the winding l such as is indicated at 38 in Fig. 4 of the a drawing may be provided. Such a .conducting iln or member may be made of aluminum and may be connected to a plurality of the cylinders such as 36 and 31. The important requirement is that suflicient cooling of the insulation be provided adjacent the end'oi the winding so that fusing or coherence is prevented to the extent that the insulation will not be torn away from the conductor when the fine adjustment in inductance is made.

The enlarged view-of the end of the winding shown in Fig. 6 of the drawing clearly indicates the effect of the cooling means or the heat conducting cylinder 36. Actually, for the length X of the conductor, the adjacent layers of insulation are cooled suiliciently during the heating process so that weldlngiusing or cohering to an extent such that the insulation would be torn away from the conductor in the event that conductor H were pulled away tor the distance X does not occur and the desired fine adjustment of inductance can be made without in any way impairing the insulation.

The antenna I0 is well adapted to be mounted on the back of the radio cabinet in any suitable manner. Also, the completed winding 10, when properly manufactured in accordance with the above description, almost looks like a spirallycan be obtained by using an uninsulated wire and inte'rwinding it with a thermoplastic tape or strip, fed from a separate reel or spool. In view of the detailed description included above it is believed that theprocess and apparatus of the present invention will be obvious to those skilled in the art.

It should be understood that the present invention is not limited to the particular apparatus and process disclosed and described in detail above and that changes and modifications may occur to those skilled in the art without departing from the spirit and scope of the present invention. It is, therefore, aimed in the appended claims to cover all such changes and modifications.

I claim:

1. The process of making a coil which com prises arranging a conductor insulated with a I jacent a predetermined small portion of said winding so that a physical juncture does not occur at said predetermined portion.

2; The process of making a coil having a predetermined inductance which comprises arranging a conductor insulated witha thermoplastic or thermosetting material in the form of a winding with the insulation of each turn of said winding in physical engagement with the insulation of at least one adjacent turn, subjecting said winding to a heating eflect toiuse the insulation of each turn with the insulation of the adjacent turn at the physical juncture between said turns, and cooling the insulation adjacent one end of the winding so that a physical juncture does not occur for a short distance at said one end.

3. The process of making a coil having a predetermined inductance which comprises arranging a conductor insulated with a thermoplastic or thermosetting material in the form of a winding with the insulation oi each turn of said winding in physical engagement with the insulation of at least one adjacent turn, subjecting saidwinding to a heating eflect to fuse the insulation of each turn with the insulation of the adjacent turn at the physical juncture between said turns by passing a predetermined current through said winding for a predetermined time, and cooling the insulation adjacent one end of the winding so that a physical juncture does not occur for a short distance at the end whereby a predetermined small length of winding may be pulled at one end 01' said winding to prevent coherence whereby a small predetermined length of said winding may be pulled away for adjusting the inductance of said winding without tearing the insulation away from said conductor.

5. The method of constructing a winding which comprises arranging a length of wire insulated with a thermoplastic material into a spirally wound coil with the insulation of adjacent turns in mutual engagement, heating the insulation of said winding for a predetermined time to cause coherence of the insulation of adjacent turns so that said winding becomes self supporting, -and cooling a short portion of the insulation at one end of said winding to prevent coherence whereby a' small predetermined length of said winding may be removed for adjusting the inductance of said winding without impairing the insulation of the remaining winding.

PAT A. DORIO.

REFERENCES CITED The followingreferences, are of record in the file of this patemt:

I UNITED STATES PATENTS Number Name Date 475,183 Burton May 17, 1892 1,606,393 Apple -2 Nov. 9, 1926 1,681,736 ,Kull Aug. 21, 1928 1,739,246 Majce -2 Dec. 10, 1929 1,874,723 Dawson Aug. 30, 1932 2,177,260 Laube Oct. 24, 1939 2,193,770 Piercy Mar. 12, 1940 2,241,282 Wackerle May 6, 1941 2,282,759

Gavitt May 12, 1942 

